Transient neurogenesis in ischemic cortex from Sox2^(+)astrocytes

The adult cortex has long been regarded as non-neurogenic.Whether injury can induce neurogenesis in the adult cortex is still controversial.Here,we report that focal ischemia stimulates a transient wave of local neurogenesis.Using 5′-bromo-2′-deoxyuridine labeling,we demonstrated a rapid generation of doublecortin-positive neuroblasts that died quickly in mouse cerebral cortex following ischemia.Nestin-Cre^(ER)-based cell ablation and fate mapping showed a small contribution of neuroblasts by subventricular zone neural stem cells.Using a mini-photothrombotic ischemia mouse model and retrovirus expressing green fluorescent protein labeling,we observed maturation of locally generated new neurons.Furthermore,fate tracing analyses using PDGFRα-,GFAP-,and Sox2-Cre^(ER) mice showed a transient wave of neuroblast generation in mild ischemic cortex and identified that Sox2-positive astrocytes were the major neurogenic cells in adult cortex.In addition,a similar upregulation of Sox2 and appearance of neuroblasts were observed in the focal ischemic cortex of Macaca mulatta.Our findings demonstrated a transient neurogenic response of Sox2-positive astrocytes in ischemic cortex,which suggests the possibility of inducing neuronal regeneration by amplifying this intrinsic response in the future.